What about all the mystical new features that would give other gameplay options than owning thiefs and mass recruit/hort troops/gold?
Like 70% of the playerbase is EU? Well, shortage of something (e.g. space, resources) produces more thieves, bandits, raiding parties and most of the time new technologies to bypass the shortage.
I guess, if there was more to do, people wouldn't be so eager about owning a thief. Yah, I know that's not true and never gonna happen.